Robert G. Greenberg, M.D. is a dermatologist located in San Ramon, CA. We have 2 locations to serve the East Bay: SAN RAMON: 5201 Norris Canyon Rd. Ste. You’ll find a lot of valuable information on the web site about skin problems, diagnoses and treatments. Robert Greenberg is a practicing Dermatology doctor in San Ramon, CA. Verna-Lou Tan is a practicing Dermatology doctor in San Ramon, CA.